Self-aligned optical grid on image sensor

ABSTRACT

An image sensor includes a substrate, a plurality of light sensitive pixels, a first plurality of color filters, a plurality of reflective sidewalls, and a second plurality of color filters. The light sensitive pixels are formed on said substrate. The first plurality of color filters is disposed over a first group of the light sensitive pixels. The reflective sidewalls are formed on each side of each of the first plurality of color filters. The second plurality of color filters are disposed over a second group of light sensitive pixels and each color filter of the second plurality of color filters is separated from each adjacent filter of said first plurality of color filters by one of the reflective sidewalls. In a particular embodiment an etch-resistant layer is disposed over the first plurality of color filters and the second group of light sensitive pixels.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates generally to color image sensors. Moreparticularly, it relates to image sensors having a light filter arraywith an optical grid for minimizing pixel cross-talk.

Description of the Background Art

Image sensors that are able to capture colored images are well known inthe prior art. Such image sensors include a plurality of light sensitiveregions (e.g. photodiodes) and a plurality of variously colored lightfilters. Each pixel includes a light filter of a single color disposedover the photodiode, which is connected to readout circuitry fordetermining the amount of light (within the spectrum corresponding tothe color of the light filter) that impinges on the pixel during ashutter period. The pixels are typically arranged in rows and columns,with a red pixel (i.e. one having a color filter adapted to pass redlight), a blue pixel, and two green pixels making up each 2×2 square ofpixels (i.e. a Bayer filter pattern). By measuring how much light ofeach color impinges on a specific region of the image sensor, coloredimages can be captured. The quality of the images depends on howaccurately the light of each color is measured by the light sensitiveregions.

Crosstalk between pixels (e.g., light filtered by one pixel but measuredby another, differently colored pixel) diminishes the accuracy ofmeasurement and causes undesirable distortions in the colors of thecaptured images. To prevent crosstalk, U.S. Patent Publication2007/0238034 (Holscher, Jr.) discloses a method of forming an opaquespacer between adjacent color filters, which blocks or reflects lightthat would otherwise travel through the color filter of one pixel andonto the light sensitive region of another. The opaque spacersignificantly decreases crosstalk between adjacent pixels, but isapproximately 50 nm thick and, therefore, reduces the quantum efficiency(QE) of each pixel.

U.S. Patent Publication 2012/0019695 (Qian et al.) discloses a colorfilter sidewall for preventing crosstalk between adjacent pixels.However, the sidewall of Qian et al. also reduces QE, because thesidewall is dark and absorbs incident light. Because some of the lightincident on each pixel is absorbed, the sensitivity of the pixels isdiminished, making the image sensor less effective for certainapplications.

U.S. Pat. No. 8,610,229 (Hsu et al.) discloses a reflective shieldingfeature comprising metal layers and a dielectric layer. However, thereflective shielding of Hsu et al. must be aligned separately from thecolor filters, requiring extra processes and increasing the cost tomanufacture.

U.S. Pat. No. 8,269,264 (Nozaki et al.) discloses a waveguidewith/without a metal section disposed between adjacent color filters.The waveguide has an index of refraction that is smaller than theindices of refraction of the color filters, which causes stray light tobend back toward the photosensitive area of the pixel. However, theimage sensor disclosed by Nozaki et al. utilizes the effect of totalinternal reflection, which occurs for light incident at specific angles.For light incident at other angles, the QE of the image sensor of Nozakiet al. is diminished, making it unsuitable for some applications.

Although several image sensors have been proposed to decrease the amountof crosstalk between adjacent pixels of different colors, each imagesensor suffers from a reduction in QE or a significant increase in timeand/or cost of production. What is needed, therefore, is a colored imagesensor that minimizes crosstalk between adjacent, differently coloredpixels and maximizes QE, while minimizing production time and/or cost.

SUMMARY

The present invention overcomes the problems associated with the priorart by providing an image capture device with reflective walls disposedbetween adjacent color filters. A method of forming the reflectivesidewalls, while eliminating at least one photomasking step is alsodisclosed. Features of the invention provide improved light efficiency,reduced inter-color crosstalk, and a simpler, self-aligningmanufacturing process.

An example method of manufacturing an image sensor includes providing asubstrate including a plurality of light sensitive pixels, forming afirst plurality of color filters over a first group of the plurality oflight sensitive pixels; and forming reflective side walls on sidesurfaces of the color filters of the first plurality of color filters.The example method further includes forming a second plurality of colorfilters over a second group of the plurality of light sensitive pixels,such that each filter of the second plurality of color filters isseparated from each adjacent filter of the first plurality of colorfilters by one of the reflective sidewalls.

In a particular example method, the step of forming the reflectivesidewalls includes forming an etch-resistant layer over the firstplurality of color filters and in gaps therebetween and forming areflective layer over the etch-resistant layer. The particular examplemethod additionally includes etching the reflective layer to remove thereflective layer from above the first plurality of color filters andfrom bottoms of the gaps, leaving a portion of the reflective layer (thereflective side-walls) on the side surfaces of the color filters of thefirst plurality of color filters. In the example embodiment, theetch-resistant layer that is less than 12 nm thick and greater than 8 nmthick. The reflective layer is less than 150 nm thick and greater than50 nm thick.

In various embodiments, the etch-resistant layer and/or the reflectivelayer can be formed from different materials. For example, in onemethod, the etch-resistant layer includes a dielectric material and thereflective layer includes a metal layer. More particularly, the metallayer includes tin nitride, and the dielectric material includes silicondioxide. In another particular method, the metal layer includestungsten, and the dielectric material includes silicon dioxide. In yetanother particular embodiment, the metal layer includes aluminum, andthe dielectric material includes silicon dioxide.

Example processes for forming the etch-resistant layer are alsodisclosed. For example, in one method, the step of forming anetch-resistant layer over the first plurality of color filters and inthe gaps includes forming the etch-resistant layer at a temperaturecooler than 225 degrees Celsius. In one particular example method, thestep of forming the etch-resistant layer at a temperature cooler than225 degrees Celsius includes forming the etch-resistant layer using achemical vapor deposition process (low temperature CVD). Alternatively,the step of forming the etch-resistant layer at a temperature coolerthan 225 degrees Celsius includes forming the etch-resistant layer usinga physical vapor deposition process (low temperature PVD).

Due to the positioning of the first plurality of color filters, three ormore differently colored filters can be formed on the image sensor. Inan example method, the step of forming a first plurality of colorfilters over the first group of the light sensitive pixels includesforming the first plurality of color filters from a material operativeto pass light of a first predetermined color band. The step of formingthe second plurality of color filters includes forming the secondplurality of color filters from a material operative to pass light of asecond predetermined color band different from the first predeterminedcolor band. The example method additionally includes forming a thirdplurality of color filters over a third group of the plurality of lightsensitive pixels, such that each filter of the third plurality of colorfilters is separated from each adjacent filter of the first plurality ofcolor filters by one of the reflective sidewalls. The step of formingthe third plurality of color filters includes forming the thirdplurality of color filters from a material operative to pass light of athird predetermined color band different from the first predeterminedcolor band and the second predetermined color band.

In the example methods, the step of forming reflective sidewalls on theside surfaces of the color filters of the first plurality of colorfilters includes forming the reflective sidewalls to extend at least ashigh as a top surface of one of the color filters of the first pluralityof color filters. The height of the reflective sidewalls increases theoptical sensitivity and decreases cross talk between adjacent lightsensitive pixels in the image sensor.

An example image sensor includes a substrate, a plurality of lightsensitive pixels formed in the substrate, a first plurality of colorfilters, a plurality of reflective sidewalls, and a second plurality ofreflective sidewalls. The color filters of the first plurality of colorfilters are disposed over a first group of the plurality of lightsensitive pixels. The reflective sidewalls are each disposed on a sidesurface of the color filters of the first plurality of color filters.Color filters of the second plurality of color filters are disposed overa second group of the plurality of light sensitive pixels, betweenadjacent filters of the first plurality of color filters. Each colorfilter of the second plurality of color filters is separated from eachadjacent color filter of the first plurality of color filters by one ofthe reflective sidewalls.

The example image sensor further includes an etch-resistant layerdisposed over top surfaces of the color filters of the first pluralityof color filters, between the reflective sidewalls and the side surfacesof the color filters of the first plurality of color filters, and over asurface of the substrate in gaps between adjacent ones of the colorfilters of the first plurality of color filters. The transparentetch-resistant layer is less than 12 nm thick and greater than 8 nmthick, and the reflective layer is less than 150 nm thick and greaterthan 50 nm thick. In a particular example embodiment, the reflectivelayer includes a metal layer, and the etch-resistant layer includes adielectric material. For example, in one embodiment, the metal layerincludes tin nitride, and the dielectric material is silicon dioxide. Inanother example embodiment, the metal layer includes tungsten, and thedielectric material is silicon dioxide. In yet another exampleembodiment, the metal layer includes aluminum, and the dielectricmaterial is silicon dioxide.

In an example image sensor, each color filter of the first plurality ofcolor filters is operative to pass light of a first predetermined colorband (e.g., green), and each filter of the second plurality of colorfilters is operative to pass light of a second predetermined color band(e.g., red) different from the first predetermined color band. Theexample image sensor further includes a third plurality of colorfilters. The color filters of the third plurality of color filters aredisposed over a third group of the plurality of light sensitive pixels,between adjacent filters of the first plurality of color filters. Eachcolor filter of the third plurality of color filters is separated fromeach adjacent color filter of the first plurality of color filters byone of the plurality of reflective sidewalls. Each filter of the thirdplurality of color filters is operative to pass light of a thirdpredetermined color band (e.g., blue) different from the firstpredetermined color band and the second predetermined color band.

In the example embodiments, each of the plurality of reflectivesidewalls extends at least as high as a top surface of a filter of thefirst plurality of color filters. In addition, because the side surfaceof the color filters of the second plurality of color filters are notdisposed adjacent the side surfaces of the color filters of the thirdplurality of color filters, a single deposition of reflective sidewallson the side surfaces of the color filters of the first plurality ofcolor filters is sufficient to separate each color filter of the displayfrom all adjacent color filters of the display with a reflectivesidewall.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the followingdrawings, wherein like reference numbers denote substantially similarelements:

FIG. 1 is a perspective view of an example camera module;

FIGS. 2A-2C are top views of a representative portion of an exampleimage sensor of FIG. 1 in various states of production;

FIG. 3 is cross-sectional view of a portion the image sensor of FIG. 1,taken along line A-A of FIG. 2C;

FIGS. 4A-4F are cross sectional views of the image sensor of FIG. 1,taken along line A-A, at various times throughout the manufacturingprocess;

FIG. 5 is a flow chart illustrating an example method of manufacturingthe image sensor of FIG. 1

FIG. 6. is a flowchart summarizing an example method of performing athird step (forming reflective side walls) of the method of FIG. 5.

DETAILED DESCRIPTION

The present invention overcomes the problems associated with the priorart, by providing an image sensor including a reflective sidewallbetween adjacent color filters and methods of producing the same. In thefollowing description, numerous specific details are set forth (e.g.,layout of color filters, semiconductor fab processes, etc.) in order toprovide a thorough understanding of the invention. Those skilled in theart will recognize, however, that the invention may be practiced apartfrom these specific details. In other instances, details of well-knownimage sensor production practices (e.g., etching, doping,chemical/physical vapor deposition, routine optimization, etc.) andcomponents have been omitted, so as not to unnecessarily obscure thepresent invention.

FIG. 1 is a perspective view of an image sensor 100 mounted on a portionof a printed circuit board (PCB) 102 that represents a PCB of a camerahosting device (e.g., automobile, manufacturing machine, medical device,cell phone, etc.). Image sensor 100 communicates electronically withother components of the hosting device via a plurality of conductivetraces 104. In the example embodiment, image sensor 100 is depicted asbeing part of a camera module 106 that further includes an opticalassembly 108 and a housing 110. As shown, housing 110 is mounted toimage sensor 100 and optical assembly 108 is disposed therebetween.Those skilled in the art will recognize that the particular designsand/or presence of PCB 102, traces 104, optical assembly 108, and/orhousing 110 will depend on the particular application, and are notparticularly relevant to the present invention. Therefore, PCB 102,traces 104, optical assembly 108, and housing 110 are representationalin character only.

FIG. 2A is a top view of a representative portion 200 of image sensor100, in an intermediate state of production. A plurality of green (G)color filters 202 are formed on image sensor 100 over an array ofphotosensitive pixels (not shown). Green color filters 202 are formed ina checkerboard pattern, defining a plurality of gaps 204 therebetween.Only some of the green color filters 202 and gaps 204 are labeled withnumeric indices, so as not unnecessarily obscure the drawing. However,all of the green color filters are labeled with the letter “G”, and allof the gaps are left blank. Green color filters 202 can be formed by anyof various processes known in the art, such as, but not limited to,spin-coating image sensor 100 with green color filter material,patterning a photoresist layer over certain portions of the green colorfilter material, and etching the green color filter material to removeportions that are not protected by the photoresist layer.

Reflective sidewalls 206 are formed on each side of each green colorfilter 202, by a process that will be described in greater detail withreference to FIGS. 4A-4F. Reflective sidewalls 206 of only one examplegreen color filter 202 are labeled, to avoid needlessly complicating thedrawing, but a reflective sidewall 206 is formed on each side of eachgreen color filter 202 adjacent a gap 204.

FIG. 2B shows image sensor portion 200 after a plurality of red colorfilters 208 have been formed in half of gaps 204. Red color filters 208are formed using substantially similar processes to those used to formgreen color filters 202, but with a material having the appropriatecolor sensitivity for a red filter.

FIG. 2C shows image sensor portion 200 after a plurality of blue colorfilters 210 have been formed in the remainder of gaps 204. Blue colorfilters 210 are formed using processes substantially similar to thoseused to form green color filters 202 and red color filters 208, but witha material having the appropriate color sensitivity for a blue filter.

FIGS. 2A-2C are intended to simply illustrate the arrangement of colorfilters 202, 208, and 210 and reflective walls 206. The formation ofcolor filters described with reference to FIGS. 2A-2C need not beperformed in the sequence described. For example, green color filters200 can be formed after red and blue color filters 204 and 206.Additionally, the layout of color filters 200, 204, and 206 on imagesensor 100 is representative in nature. The present invention can beutilized with varying layouts, differently shaped pixels/color filters,and/or with differently colored filters. The particular details providedare by way of example and not limiting with respect to the scope of theinvention.

FIG. 3 is a sectional view of an even smaller portion 300 of imagesensor 100 taken along line A-A of FIG. 2C. Portion 300 includes aportion of a substrate 302, a portion of pixel circuitry 304, an oxidelayer 306, and pixel optics 308. In the example embodiment, substrate302 is a p-doped silicon wafer, formed by diffusing any of a number ofcharge donor atoms into a silicon crystal or other applicable crystallattice. Pixel circuitry 304 includes photodiodes, transistors,diffusion regions, metallization layers, and any other necessaryelectronics that have been formed onto substrate 302, to create aphotosensitive array of image sensor 100. Oxide layer 306 is apassivation layer that prevents decay of pixel circuitry 304 andprotects pixel circuitry 304 from damage during the formation of pixeloptics 308. In the example embodiment, oxide layer 306 is a silicondioxide layer, but can be formed from any other suitable material.

Pixel optics 308 impart color sensitivity to image sensor 100, decreasepixel cross-talk, and increase the quantum efficiency (QE) of theindividual pixels 309 that make up image sensor 100. Pixel optics 308(shown in FIG. 3) include green color filters 202, a red color filter208, an etch-resistant layer 310, reflective sidewalls 206, andmicro-lenses 314. Green color filters 202 filter incident light and passonly light corresponding to the green range of the visible lightspectrum. Red color filter 204 passes only light corresponding to thered range of the visible light spectrum. Utilizing differently coloredfilters allows image sensor 100 to produce full-color images by blendingthe registered light intensity values detected by the pixels disposedbeneath each set of four color filters (1 Red, 1 Blue, and 2 Green)during any given shutter period.

Etch-resistant layer 310 allows for the self-alignment of reflectivesidewalls 206, and prevents damage to green color filters 202 during themanufacturing process. Etch-resistant layer 310 is a layer of silicondioxide formed before the formation of red color filters 208 and bluecolor filters 221 (FIG. 2C). Etch-resistant layer 310 is approximately10 nanometers (nm) thick (thickness can vary between 8 nm and 12 nm),which is thin enough to transmit visible light. Because reflectivesidewalls 206 are the same height as color filters 200, 204 and 206,they prevent pixel crosstalk by reflecting filtered light down and intothe intended photosensitive region of pixel circuitry 304. As the arrowsin FIG. 3 illustrate, reflective sidewalls 206 reflect light from eithersurface (e.g., the surface facing green light filter 202 or the surfacefacing red light filter 208). Reflective sidewalls 206 are about 100 nmthick (thickness can vary between 50 nm and 150 nm). While reflectivesidewalls can vary in thickness, it is beneficial for the ratio betweenthe height and the width to stay sufficiently high to allow propercontrol of the grid profile during manufacturing. Additionally, if thewall is too thick a large percentage of incident light is reflected fromthe top of each of reflective sidewalls 206 and lost. Assuming constantheight, the thinner reflective sidewalls 206 are, the higher the QE ofthe corresponding pixel will be, as long as reflective sidewalls 206 arenot made so thin as to be rendered transparent. Micro-lenses 314 aredisposed above each of green, red and blue color filters 200, 204 and206. Micro-lenses 314 refract incident light and direct it toward thecenter of the associated photodiode, thereby further increasing QE.

In the example embodiment, reflective sidewalls 206 are formed from tinnitride. In alternate embodiments, reflective sidewalls 206 can beformed from tungsten, aluminum, or other reflective material, assumingthe material can be deposited in sufficiently thin layers. Additionally,reflective sidewalls can be formed from multiple layers, such as adielectric layer and a metal layer. Alternatively, reflective sidewalls206 can be sandwiched between two oxide layers. In such an embodiment,the second oxide layer would be deposited after reflective sidewalls 206are formed. The second oxide layer can be thinner, because it does notneed to function as an etch stop layer. The second oxide layer providesincreased protection for image sensor 100.

FIGS. 4A-4F illustrate an example process for forming color filters onan image sensor. FIG. 4A shows portion 300, including substrate 302,pixel circuitry 304, oxide layer 306, and green color filters 202. Asexplained above, green color filters 202 are formed using knownprocesses.

FIG. 4B shows portion 300 after etch-resistant layer 310 has been formedon the top and side surfaces of green color filters 200 and on oxidelayer 306 in one of gaps 204. In the example embodiment, etch-resistantlayer 310 is a silicon oxide layer (e.g., silicon dioxide SiO₂) formedby a low temperature (˜200 C) chemical vapor deposition (CVD), with athickness of approximately 10 nm. The thickness of etch-resistant layercan be varied as long as the layer remains transparent to the relevantwavelengths of light. In alternate embodiments, etch-resistant layer 310can be formed by any of a number of processes, including, but notlimited to, CVD, physical vapor deposition (PVD), etc.

FIG. 4C shows portion 300 after a reflective layer 400 has been formedover etch-resistant layer 310. In the example embodiment, reflectivelayer 400 is a metal layer (e.g., W, TiN, etc.) formed by PVD. Inalternate embodiments, reflective layer 400 can be formed by otherknown, suitable processes.

FIG. 4D shows portion 300 after most of reflective layer 400 has beenremoved by an anisotropic dry etch directed from top to bottom. Becausethe ratio between the height of reflective sidewalls and the thicknessof reflective layer 400 is large, the anisotropic etch leaves reflectivesidewalls 206 in place, but removes reflective layer 400 from the topsurfaces of green color filters 200 and the portion of etch-resistantlayer 310 in the bottom of gap 204. Reflective layer 400 can be removedby any of a number of known, suitable processes, including, but notlimited to, dry etching, wet etching, and so on.

FIG. 4E shows portion 300 after a red color filter 208 has been formedinto gap 204. In a similar but separate step, which is not illustratedin FIG. 4E, blue color filters 210 are formed in a remaining group ofgaps 204, which do not contain a green color filter 202 or a red colorfilter 208.

FIG. 4F shows portion 300 after micro-lenses 314 have been formed on topof green color filters 200 and red color filter 204.

FIG. 5 is a flow chart summarizing an example method 500 ofmanufacturing an image sensor. In a first step 502, a substrateincluding a plurality of light sensitive pixels is provided. Then, in asecond step 504, a first plurality of color filters is formed over afirst group of the plurality of light sensitive pixels. Then, in a thirdstep 506, reflective sidewalls are formed on side surface of the colorfilters of the first plurality of color filters. Next, in a fourth step508, a second plurality of color filters is formed over a second groupof the plurality of light sensitive pixels, adjacent the first pluralityof color filters. Then, in a fifth step 510, a third plurality of colorfilters over a third group of the plurality of light sensitive pixels,adjacent the first plurality of color filters and the second pluralityof color filters.

FIG. 6. is a flowchart summarizing an example method 600 of performingthird step 506 (forming reflective side walls) of method 500 of FIG. 5.In a first step 602, an etch-resistant layer is formed over the firstplurality of color filters and in the gaps therebetween. Next, in asecond step 604, a reflective layer is formed on the etch-resistantlayer. Then, in a third step 606, the reflective layer is etched toremove the reflective layer above the first plurality of color filtersand in the gaps, leaving a reflective sidewall on the side surfaces ofthe first plurality of color filters.

The description of particular embodiments of the present invention isnow complete. Many of the described features may be substituted, alteredor omitted without departing from the scope of the invention. Forexample, alternate color schemes (e.g. Yellow-Magenta-Cyan) can be usedin place of the RGB scheme described. As another example, the presentinvention can be utilized to eliminate pixel crosstalk in image sensorswith alternate pixel shapes (e.g. hexagonal) and/or structures. Theseand other deviations from the particular embodiments shown will beapparent to those skilled in the art, particularly in view of theforegoing disclosure.

1. A method of manufacturing an image sensor, said method comprising:providing a substrate including a plurality of light sensitive pixels;forming a first plurality of color filters over a first group of saidplurality of light sensitive pixels; forming reflective side walls onside surfaces of said color filters of said first plurality of colorfilters; and forming a second plurality of color filters over a secondgroup of said plurality of light sensitive pixels, such that each filterof said second plurality of color filters is separated from eachadjacent filter of said first plurality of color filters by one of saidreflective sidewalls; and wherein said step of forming said reflectivesidewalls includes forming an etch-resistant layer over said firstplurality of color filters and in gaps therebetween, forming areflective layer over said etch-resistant layer, and etching saidreflective layer to remove said reflective layer from above said firstplurality of color filters and from bottoms of said gaps, leaving aportion of said reflective layer on said side surfaces of said colorfilters of said first plurality of color filters.
 2. (canceled)
 3. Themethod of claim 1, wherein said step of forming an etch-resistant layerover said first plurality of color filters and in said gaps includesforming an etch-resistant layer that is less than 12 nm thick andgreater than 8 nm thick.
 4. The method of claim 3, wherein said step offorming a reflective layer over said etch-resistant layer includesforming a reflective layer that is less than 150 nm thick and greaterthan 50 nm thick.
 5. The method of claim 1, wherein: said etch-resistantlayer includes a dielectric material; and said reflective layer includesa metal layer.
 6. The method of claim 5, wherein: said metal layerincludes tin nitride; and said dielectric material includes silicondioxide.
 7. The method of claim 5, wherein: said metal layer includestungsten; and said dielectric material includes silicon dioxide.
 8. Themethod of claim 5, wherein: said metal layer includes aluminum; and saiddielectric material includes silicon dioxide.
 9. The method of claim 1,wherein said step of forming an etch-resistant layer over said firstplurality of color filters and in said gaps includes forming saidetch-resistant layer at a temperature cooler than 225 degrees Celsius.10. The method of claim 9, wherein said step of forming saidetch-resistant layer at a temperature cooler than 225 degrees Celsiusincludes forming said etch-resistant layer using a chemical vapordeposition process.
 11. The method of claim 9, wherein said step offorming said etch-resistant layer at a temperature cooler than 225degrees Celsius includes forming said etch-resistant layer using aphysical vapor deposition process.
 12. The method of claim 1, whereinsaid step of forming a first plurality of color filters over said firstgroup of said light sensitive pixels includes forming said firstplurality of color filters from a material operative to pass light of afirst predetermined color band.
 13. The method of claim 12, wherein saidstep of forming said second plurality of color filters includes formingsaid second plurality of color filters from a material operative to passlight of a second predetermined color band different from said firstpredetermined color band.
 14. The method of claim 13, furthercomprising: forming a third plurality of color filters over a thirdgroup of said plurality of light sensitive pixels, such that each filterof said third plurality of color filters is separated from each adjacentfilter of said first plurality of color filters by one of saidreflective sidewalls; and wherein said step of forming said thirdplurality of color filters includes forming said third plurality ofcolor filters from a material operative to pass light of a thirdpredetermined color band different from said first predetermined colorband and said second predetermined color band.
 15. The method of claim1, wherein said step of forming reflective sidewalls on said sidesurfaces of said color filters of said first plurality of color filtersincludes forming said reflective sidewalls to extend at least as high asa top surface of one of said color filters of said first plurality ofcolor filters. 16.-27. (canceled)